Method and device for detecting and evaluating objects in the vicinity of a motor vehicle

ABSTRACT

A method and a device are proposed for acquiring and evaluating objects in the surrounding area of a vehicle, in which, using at least one radar sensor ( 2 ), the target objects ( 5, 6; 10 ) in a monitoring area ( 1 ) are acquired, and in at least one evaluation unit the distance data and/or velocity data of the target objects ( 5, 6; 10 ) are evaluated. The acquisition of the target objects takes place within a virtual barrier ( 4; 4.1, 4.2 ) that can be modified in its distance from the vehicle ( 3 ) and in its length (Δx VB ), and, using a transmission signal of a pulse radar sensor ( 2 ), the receive signal reflected from the target object ( 5, 6; 10 ) can be evaluated in one or more receive channels ( 20, 21 ) in such a way that different locus resolutions and different dimensions with respect to distance and length (Δx VB ) of the virtual barrier ( 4; 4.1, 4.2 ) can be achieved.

BACKGROUND INFORMATION

[0001] The invention relates to a method and to a device for acquiring and evaluating objects in the area surrounding a vehicle, using a radar sensor according to the preamble of the method claim and of the device claim.

[0002] For example, from German Patent 44 42 189 A1 it is known that in a system for distance measurement in the surrounding area of motor vehicles, sensors having transceiver units are used for the simultaneous transmission and reception of information. With the aid of the distance measurement, here passive protective measures for the vehicle can be activated, for example in case of a front, side, or rear collision. With an exchange of the acquired information, for example a judgement of traffic situations can be carried out for the activation of corresponding triggering systems.

[0003] In addition, regarded in itself it is generally known that a distance measurement can be carried out using what is known as a pulse radar system, in which a pulse carrier is sent out having a rectangular envelope of an electromagnetic oscillation, e.g. in the gigahertz range. This pulse carrier is reflected at the target object, and from the time from the transmission of the impulse and the impinging of the reflected radiation, it is possible to easily determine the distance to the goal, and (with limitations), using the Doppler effect, the relative speed of the target object as well. Such a measurement design is for example described in the textbook by A. Ludloff, “Handbuch Radar und Radarsignalverarbeitung,” pages 2-21 to 2-44, Vieweg Verlag, 1993.

[0004] The design of such a known radar sensor is constructed in such a way that the radar pulses reflected at the respective target object travel to a receiver via antennas, and there they are mixed with the time-delayed pulses provided by the pulse production system. After a low-pass filtering and analog/digital conversion, the output signals of the receiver are supplied to an evaluation unit.

[0005] For the reliable controlling of the above-mentioned passenger protection systems in a motor vehicle, as a rule a multiplicity of radar sensors is required for the individual conflict situations in the area surrounding the motor vehicle. For example, a collision early recognition (pre-crash recognition) system is necessary in order to enable an early acquisition of an object that represents a danger for the vehicle occupants in case of a collision. In this way, it should be possible to activate protective systems such as an airbag, seat-belt tensioner, or sidebag at the proper time to achieve the greatest protective effect.

[0006] For a proper triggering of these safety systems in the motor vehicle, the knowledge of the relative velocity (speed) between the actual motor vehicle and one or more targets (e.g., vehicles traveling ahead, obstacles) before and during an anticipated collision, and of the expected time of the collision, is of great importance.

[0007] Using a radar sensor of the type mentioned above, in a known manner methods can be carried out, for example using a pulse radar sensor or what is known as an FMCW radar sensor, that enable an acquisition and evaluation of the relative velocity. Such an FMCW radar device is described for example in European Patent 0 685 930 A1.

[0008] For example, at successive times distance values can be measured and differentiated with respect to time; in this way, one obtains the values for the instantaneous relative velocity between the target and the radar sensor. Through a double differentiation of the distance values, it is also possible to obtain the values for the acceleration relative to the target. Using a different known method, the difference frequency between the transmitted oscillator frequency of the radar sensor and the signal reflected and received from the target can be produced, and what is known as the Doppler frequency can be evaluated.

[0009] From the values measured in this way, the time until the collision, and also, in particular with the use of a plurality of spatially distributed sensors, the components orthogonal to the front of the vehicle of the relative velocity or acceleration, and the location of the collision, can be calculated. Using the instantaneous values of the acceleration, the corresponding values for the time of the collision can then be extrapolated.

[0010] In this context, a high degree of measurement precision is important, in particular given targets having a low reflection cross-section and given high disturbing signal portions in the velocity range that is to be evaluated for the respective application (e.g., triggering of the seat-belt tensioner or changing over of the stages of the airbag). Here, previous measurement methods are based on a constant length of the acquisition area (region) in the area being monitored, and/or a constant distance from this area to the radar sensor.

ADVANTAGES OF THE INVENTION

[0011] A method and device for acquiring and evaluating objects in the surrounding area of a vehicle using a radar sensor of the type indicated above is advantageously developed according to the invention in that in a monitoring area (monitored area or monitored region) the acquisition of the target objects takes place within a virtual barrier, known as a “range gate,” that can be modified in its distance from the vehicle and in its length.

[0012] After an evaluation of the targets acquired using a radar sensor with respect to their potential risk, here the distance and the velocity, as well as, if necessary, the acceleration relative to the target object are measured. Using the adaptive construction of the dimensions of the virtual barrier according to the present invention, the measurement process is advantageously optimized with respect to measurement precision, locus resolution, and the signal/noise ratio.

[0013] In a preferred specific embodiment of the method according to the present invention, using a transmission signal of a pulse radar sensor, the received signal reflected from the target object is evaluated in at least two receive channels in such a way that different locus resolutions and different dimensions with respect to distance and length of the virtual barrier are achieved.

[0014] In a first receive channel, the received signal for the acquisition of the distance of the target objects is processed using a reference signal having a fixedly set pulse duration τ_(s) corresponding to the transmission signal. In a second receive channel, the receive signal is advantageously processed using a reference signal having a modifiable pulse duration τ_(R), either for the measurement of the distance with a modifiable locus resolution or for setting the length Δx_(VB), of the virtual barrier.

[0015] The method according to the present invention can be executed in particularly advantageous fashion if the method steps a) to d) indicated in subclaim 4 are executed, which are also described in their mathematical relationships on the basis of FIG. 3 of the drawing, in the explanation of the exemplary embodiment. In addition, the method according to the present invention can advantageously be developed if the features of the subclaims that are dependent on subclaim 4 are also executed.

[0016] A particularly advantageous device for the execution of the method according to the present invention is indicated in apparatus claim 10 and in the additional apparatus claims dependent thereon, in which a pulse radar sensor, having in particular a first receive channel for distance measurement and a second receive channel for setting the virtual barrier in the sense previously described, is constructed.

[0017] The adaptive setting of the length Δx_(VB)=Δx_(mess) of the virtual barrier enables, in a simple manner, an optimization of the value for Δx_(mess) with respect to measurement precision, locus resolution, and the signal/noise ratio. Given a high velocity relative to the vehicle, target objects having a low reflection cross-section are recognized, because in this case a greater value is used for the length of the virtual barrier.

[0018] The setting of a distance of the virtual barrier to the radar sensor that is as small as possible, with as low a value as possible for the length Δx_(VB), has the following advantages over larger values for the distance:

[0019] If the vehicle and the target object move past one another, the probability that a target object moves through the virtual barrier with a high relative velocity is lower; in this way, false triggerings or false measurements become less probable.

[0020] The signal/noise ratio is larger given a smaller distance of the target object to the radar sensor, and also allows the detection or measurement of target objects having a low reflection cross-section.

[0021] In addition, it is also advantageous that low target objects that are not supposed to be recognized, such as for example curbstone edges, are not acquired by the radar sensor dependent on their height, given lower values for Δx_(VB) or Δx_(mess), the constructive height of the radar sensor, and the horizontal opening angle of the radar transmission antenna or of the reception antenna.

[0022] With the method according to the present invention, the time of the measurement can advantageously be selected relative to the time of the expected collision of the vehicle with the target object, corresponding to the requirements of the applications.

[0023] This feature, and additional features of preferred developments of the invention, result from the claims and also from the specification and the drawings; the individual features can respectively be realized individually or multiply in the form of subcombinations in the specific embodiment of the invention and in other areas, and can represent advantageous and patentable embodiments, for which protection is here claimed.

DRAWING

[0024] A method according to the present invention and a device for acquiring and evaluating objects in the surrounding area of a vehicle is explained on the basis of the exemplary embodiments in the drawing.

[0025]FIG. 1 shows a drawing of a monitoring area of a radar sensor in the front area of a vehicle, having a virtual barrier for the acquisition and evaluation of a target object;

[0026]FIG. 2 shows a drawing of a monitoring area of a plurality of radar sensors on a vehicle, having a virtual barrier corresponding to FIG. 1;

[0027]FIG. 3 shows a drawing of the monitoring area according to the previous Figures, in a lateral section, and

[0028]FIG. 4 shows a block switching diagram of a pulse radar sensor with which the adaptive setting of the virtual barrier can be executed.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0029] In FIG. 1, a monitoring area 1 of a radar sensor 2 in the front area of a vehicle 3 is shown graphically, provided with a virtual barrier 4 that is explained in more detail on the basis of the following Figures. Radar sensor 2 is present for the acquisition and evaluation of target objects 5 and 6 (here indicated only as examples) in monitoring area 1 with respect to their distance from vehicle 3, and in particular also with respect to their relative velocity v_(rel) or v′_(rel) to vehicle 3.

[0030] According to the inventive realization of the proposed method for evaluating monitoring area 1, a virtual barrier 4, which can be controlled adaptively in the direction indicated with an arrow, is set up that is provided with a suitable distance from radar sensor 2, and in which distance range x_(mess) that is to be measured can be acquired. Here, virtual barrier 4 represents a subarea of monitoring area 1, and can already be realized with the aid of an individual radar sensor 2 having horizontal opening angle β.

[0031] In a modification of the drawing according to FIG. 1, in FIG. 2 a multiplicity of radar sensors 2.1, 2.2, 2.3, and 2.4 are arranged in the front area of vehicle 3 and also laterally. Here it can be seen that in particular target object 6 is acquired by radar sensor 2.2 with a relative velocity v′_(rel/b), and is acquired by radar sensor 2.3 with a relative velocity v′_(rel/a). At the front of vehicle 3, there thus results an orthogonal relative velocity v′_(orth).

[0032] On the basis of the drawing according to FIG. 3, in a lateral representation of monitoring area 1 it is shown that adaptively controllable virtual barrier 4 can be set up in such a way that for particular situations it is provided with a suitable distance to radar sensor 2 and with a suitable length x_(mess). For example, here a virtual barrier 4.1 is shown for a high velocity in the more distant area for the measurement of the distance within Δx_(mess1), and a virtual barrier 4.2 is shown for a relatively low velocity in the closer area, for the measurement of the distance within Δx_(mess2).

[0033] The determination of the spatial dimensions of virtual barriers 4.1 or 4.2, and the sequence of the measurement processes for the distance and the velocity, can here be carried out in the following method steps:

[0034] a) First, given the presence of target objects (here, for example, wall 10), distance measurements are carried out in monitoring area 1. From the values for the target distances, relative velocity v′_(rel), and, if warranted, acceleration a′_(rel) of vehicle 3 relative to the respective target object is determined.

[0035] b) Subsequently, a time interval t₀ is defined that is necessary for the realization of a signal processing on the basis of the measurement values, a data transmission, and a controlling of the relevant applications in the motor vehicle (for example, the changeover of the safety stages in the airbag, the triggering of the seat-belt tensioners, etc.). Time interval t₀ can here also be defined as a function of relative velocity v′_(rel) and/or of acceleration a′_(rel).

[0036] c) On the basis of the previously determined values, the minimum required distance x_(min) of virtual barrier 4.1 or 4.2 from radar sensor 2 can now be determined according to the following equation:

x _(min) =v′ _(rel) *t ₀ +a′ _(rel) *t ₀ ²/2   (1)

[0037] The distance X₀ of virtual barrier 4.1 or 4.2 from radar sensor 2 is here selected such that this distance does not fall below the value of x_(min).

[0038] d) Given a nearing to target object 10, the instantaneous target distance is compared with the value of the sum x_(min)+Δx_(mess). If the instantaneous distance to target 10 is smaller than x_(min)+Δx_(mess), there takes place here a velocity acquisition through a measurement of the Doppler frequency f_(d) inside virtual barrier 4.1 or 4.2, with a measurement time t_(mess). The length Δx_(VB) of virtual barrier 4.1 or 4.2 is then approximated to the value from the following equation:

Δx_(VB) ≈Δx _(mess) =v′ _(rel) *t _(mess) +a′ _(rel) *t _(mess) ²/2   (2)

[0039] Measurement time t_(mess) can here also be a function of relative velocity v′_(rel) and/or of acceleration a′_(rel).

[0040] e) The determination of the relative velocity with the aid of Doppler frequency f_(d) follows from the known equation:

f _(d) =f ₀*2v _(rel)/(c−v _(rel))   (3).

[0041] Here:

[0042] c=the velocity of light in the relevant medium,

[0043] f₀=the oscillator frequency, and

[0044] v_(rel) the relative velocity between the sensor and target object.

[0045] Derived from this, the relative velocity can be calculated according to the following equation:

v _(rel) =f _(d) *c/(f _(d)+2*f ₀)   (4)

[0046] f) In particular if the preceding calculations yield the result that V_(rel)≠v′_(rel), (cf. target objects 5 and 6 in FIG. 1), steps c) to e) can be repeated with values correspondingly adapted to v_(rel), for the distance range Δx_(VB)≈Δx_(mess) and for x_(min).

[0047] In this way, one can obtain a second value, based on the measurement of Doppler frequency f_(d), for relative velocity v_(rel2), which if necessary can be used in place of first measurement value v_(rel1). From the two values for the relative velocity, acceleration a_(rel) can then also be calculated if necessary. An expansion of the method with n-fold repetition of steps a) to e) and subsequent evaluation of measurement values v_(rel1) to v_(reln) is also possible here.

[0048] g) if relative accelerations a_(rel) or a′_(rel) have been measured, it is possible to calculate more precisely velocity v_(c) for the time of the collision, using

v _(c) =v _(rel) +a _(rel) *t _(mess)   (5)

[0049] or

v _(c) =v _(rel) +a′ _(rel) *t _(mess)   (6).

[0050] Otherwise, v_(c)=v_(rel) holds here as well.

[0051] As an alternative to method step a), the determination of relative velocity v′_(rel) and, if necessary, a′_(rel) can also take place using a cyclical monitoring of a virtual barrier 4.1 or 4.2, which takes place on the basis of the following equations (1) and (2), with the values

x _(min) =v′ _(rel max) *t ₀ +a′ _(rel max) *t ₀ ²/2   (1.1)

[0052] and

Δx _(VB) ≈Δx _(mess) =v′ _(rel max) *t _(τess) +a′ _(rel max) *t _(mess) ²/2   (2.1).

[0053] Here, values v′_(rel max) and a′_(rel max) are maximum values, that is, what are known as measurement range end values for the relative velocity and the relative acceleration between vehicle 3 and target object 10. If a target object 10 is recognized within this virtual barrier, the further sequence of the measurement method than takes place corresponding to points b) to g); i.e., an additional measurement takes place within a newly dimensioned virtual barrier 4.1 or 4.2.

[0054] Given an increase of the value for Δx_(mess), a more precise measurement of the relative velocity and acceleration can be carried out with a greater signal/noise ratio, in particular at targets having high velocity and a low reflection cross-section. However, a value that is as small as possible for Δx_(mess) is necessary in order to obtain the highest possible locus resolution. Consequently, the value for Δx_(mess) is a compromise between various, possibly opposed, requirements.

[0055] An exemplary embodiment of a circuit system for the construction of a radar sensor 2 with which an adaptive measurement method having the previously described method steps can be carried out, is explained on the basis of the block switching diagram according to FIG. 4. Although a pulse radar system is assumed in the following description of an exemplary embodiment, the method according to the present invention can also be adequately executed using an FMCW radar system.

[0056] In general, given a pulse radar system the modification of the length of virtual barrier 4, 4.1, or 4.2,takes place for example through a modification of the pulse duration or burst duration of the transmitted signal, and/or of the pulse duration of the reference signal used for cross-correlation (mixing) with the received signal. In contrast, given a pulse radar system, the position of virtual barrier 4, or 4.1 or 4.2, can be set through time-delaying of the reference signal in relation to the transmitted signal.

[0057] In the block switching diagram according to FIG. 4, two receive channels 20 and 21, having an antenna 22, or also having a second antenna (not shown) for channel 21, are present. A pulse generator 23 is provided that supplies the pulse carrier for the radar signal, which is produced by an oscillator as a radar transmitter 24.

[0058] In a branch for first receive channel 20, a first pulse duration adjustment unit 25 is present for pulse duration is, with which the signal transmitted by radar transmitter 24 is also charged. The pulse signal adjusted in this way at the output of pulse duration adjustment unit 25 is routed to a pulse input 27 of first receive channel 20, via a delay unit 26, as a reference signal for the distance measurement of target objects 5, 6, or 10. Pulse duration τ_(s) in first receive channel 20 is thus set to a constant value, and corresponds to the pulse duration of the signal of radar transmitter 24. In this way, a maximum is obtained for the signal/noise ratio (S/N), through which this receive channel 20 is used for the distance measurement with a high locus resolution.

[0059] In a second branch, behind pulse generator 23, there is a pulse duration adjustment unit 28, which can be modified in continuous fashion or in discrete fashion, for pulse duration τ_(R), and subsequent to this a delay unit 29 is also present, this pulse signal being routed to a pulse input 30 of second receive channel 21 as a reference signal for the setting of the length and position of virtual barrier 4, 4.1, or 4.2. Thus, using pulse duration adjustment unit 28, pulse duration τ_(R) can be adjusted in second receive channel 21, through which measure this channel 21 is also used for the measurement of the relative velocity between vehicle 3 and target objects 5, 6, or 10 within an adaptively modifiable virtual barrier 4, 4.1, 4.2.

[0060] Both receive channels 20 and 21 thus also permit a mutually independent adjustment of the delay for the respective pulse of the reference signal at inputs 27 and 30 of the two receive channels 20 and 21. The different values for τ_(R) and τ_(s) effect in second receive channel 21 a reduction of the signal/noise ratio S/N, which can be tolerated in particular for a measurement of the relative velocity at close range (virtual barrier 4.2 according to FIG. 3).

[0061] The demodulation of the pulse radar signals in receive channels 20 and 21 here takes place using mixing techniques that are known from the prior art, with which what are known as an I signal and a Q signal of an I/Q mixer (In phase-Quadrat-Mixer (In-phase Square Mixer)) is produced for further processing. Here, each receive channel 20 or 21 can contain both signals (I and Q) or only one signal (I or Q) For a cross-correlation in the mixer of receive channel 21, as previously mentioned, pulse duration τ_(R) is used. The length Δx_(VB) of virtual barrier 4, 4.1, 4.2 is thus calculated as

Δx _(VB)=(τ_(R)+τ_(s))c/2   (7).

[0062] According to the present invention, this length Δx_(VB) is adjusted through a corresponding modification of pulse duration τ_(R) of the reference signal at input 30 of second receive channel 21. Because τ_(s) is constant, the measurement in first receive channel 20 is not influenced.

[0063] The exemplary embodiments described here can be modified, in particular with respect to the number of receive channels or receive branches and of the receiver modules used in common or separately, without essentially modifying the function according to the present invention. A combination, deviating from the represented exemplary embodiments, of sequential and parallel evaluation of distance and velocity in one or more receive channels is likewise possible. 

What is claimed is:
 1. A method for acquiring (detecting) and evaluating objects in the area surrounding a vehicle (3), in which using at least one radar sensor (2), the target objects (5, 6; 10) in a monitoring area (1) are acquired, and the distance data and/or velocity data of the target objects (5, 6; 10) are evaluated in at least one evaluation unit, wherein the acquisition of the velocity of the target objects takes place within a virtual barrier (4; 4.1, 4.2) that can be modified in its distance (x₀) from the vehicle (3) and in its length (Δx_(VB)).
 2. The method according to claim 1, wherein, using a transmission signal of a pulse radar sensor (2), the receive signal reflected from the target object (5, 6; 10) is evaluated in one or more receive channels (20, 21) in such a way that different locus resolutions and different dimensions with respect to distance (x₀) and length (Δx_(VB)) of the virtual barrier (4; 4.1, 4.2) are achieved.
 3. The method according to claim 2, wherein in a first receive channel (20), the receive signal is processed, using a reference signal having a fixedly set pulse duration (τ_(s)) corresponding to the transmission signal, for the acquisition of the distance of the target objects (5, 6; 10), or for setting the distance (x₀) of the virtual barrier (4; 4.1, 4.2), and wherein in a second receive channel (21), the receive signal is processed, using a reference signal having a variable pulse duration (τ_(R)), for the adjustment of the length (Δx_(VB)) of the virtual barrier (4; 4.1, 4.2), or for the acquisition of the target objects (5, 6; 10) with modifiable locus resolution, or in another distance range.
 4. The method according to one of the preceding claims, wherein the following method steps are executed: a) in the monitoring area (1), an acquisition is carried out of the distance and of the relative velocity (v′_(rel)), and, if necessary, of the acceleration (a′_(rel)) of the vehicle (3) relative to the respective target object (5, 6; 10), b) a time interval (t₀) is predetermined for measurement value processing, data transmission, and controlling of the relevant application, c) the required distance (x_(min)) of the virtual barrier (4; 4.1, 4.2) from the radar sensor (2), and the length of the measurement area (x_(mess)) are determined, the distance (X₀) of the virtual barrier (4; 4.1, 4.2) from the radar sensor (2) being selected such that this distance does not fall below the minimum value (x_(min)), d) if the instantaneous target distance of the target object (5, 6; 10) is smaller than the sum (x_(min)+Δx_(mess)), there takes place here an acquisition of velocity and of acceleration (v_(rel), v′_(rel), a_(rel), a′_(rel)) through a measurement of the Doppler frequency (f_(d)) inside the virtual barrier (4; 4.1, 4.2) with a measurement time (t_(mess)).
 5. The method according to claim 4, wherein the time interval (t₀) is defined as a function of the relative velocity (v′_(rel)) and/or of the acceleration (a′_(rel)).
 6. The method according to claim 4 or 5, wherein steps c) and d) are multiply repeated, each with newly calculated values for the length of the virtual barrier (Δx_(VB)) and for the minimum distance (x_(min)), for the acquisition of a plurality of distance ranges and velocity ranges.
 7. The method according to claim 4, 5 or 6, wherein, in the case in which the previous calculations yield the result that the second measurement of the velocity (v_(rel)) of a target object (5) is smaller than the first measurement of the velocity (v′_(rel)) of the same target object, steps c) and d) according to claim 4 are repeated with lower values for the distance range (Δx_(VB)≈Δx_(mess)) and for the minimum distance (x_(min)).
 8. The method according to claim 4, 5, 6, or 7, wherein from the relative accelerations (a_(rel), a′_(rel)) between the target objects (5, 6; 10) and the vehicle (3), the velocity (v_(c)) for the time of a collision is calculated according to the equation: v _(c) =v _(rel) +a _(rel) *t _(mess) or v _(c) =v _(rel) +a′ _(rel) *t _(mess).
 9. The method according to one of the preceding claims, wherein the following method steps are executed: the measurement of the distance of the target objects (5, 6; 10) present in the monitoring area is carried out in one or more receive channels, the target objects (5, 6; 10) are selected that are relevant for an application, the relative velocity of the selected target objects (5, 6; 10) is carried out through evaluation of the Doppler frequency within the respective virtual barrier (4; 4.1, 4.2) in one or more receive channels, simultaneous with additional distance measurements in the receive channels used therefor.
 10. A device for executing the method according to one of the preceding claims, wherein a pulse radar sensor (2) has a first receive channel (20), preferably for distance measurement, and has additional receive channels (21), preferably for adjusting the virtual barrier (4; 4.1, 4.2), or likewise for distance measurement, as well as a pulse generator (23) for the production of modulated carrier pulses for the signal of a radar transmitter (24) and demodulation in the receive channels (20, 21).
 11. The device according to claim 10, wherein for the first receive channel (20), a first pulse duration adjustment unit (25) is present for the pulse duration (τ_(s)) with which the signal of the radar transmitter (24) is also charged and is routed to a pulse input (27) of the first receive channel (20) via a delay unit (26) as a reference signal, preferably for the distance measurement, and for the second receive channel (21), an adjustment unit (28) for the pulse duration (τ_(R)) is present that can be modified continuously or discretely, and a delay unit (29) is present, this pulse signal being routed, preferably as a reference signal, to a pulse input (30) of the second receive channel (21) for the adjustment of the length and of the distance of the virtual barrier (4; 4.1, 4.2), or for the distance measurement with a modifiable locus resolution.
 12. The device according to claim 10 or 11, wherein the mixer for the mixing of the transmission signal and of the signal supplied by the reception antenna (22) in the respective receive channel (20, 21) is an I/Q mixer.
 13. The device for executing the method according to one of claims 1 to 9, wherein the radar sensor (2) contains an FMCW radar system that is equipped with one or more receive channels.
 14. A method or a device according to one of the preceding claims, wherein the evaluation of the received radar signal is executed in one or more receive channels through a combination of chronologically sequential and/or chronologically parallel evaluation in the receive channels. 